1. Field of the Invention
The invention relates to a transit switch for a fast communications network by packets using the technique of asynchronous transmission, notably an ATM (asynchronous transmission mode) type of asynchronous network.
A fast communications system using packets (or cells as they are also called in ATM terminology) has a plurality of switches connected to one another by high bit-rate arteries, the switches connecting a plurality of end terminals. The different types of network switches include end switches that are directly connected to the end terminals in which the packets are shaped out of the signals generated by sender terminals, and switches known as transit switches in which the shaped packets, having travelled in transit through arteries of the network, are handled and then shunted towards one or more transit or end switches.
2. Description of the Prior Art
In the end switches, the packets are shaped so as to be constituted by a header part and an information element part. The header part identifies a destination terminal towards which the information elements contained in the packet in question have to be conveyed. The packets constituted in an end switch are then transferred through an artery to a transit switch that is connected to a plurality of packet emitting channels and to a plurality of packet receiving channels. It will be understood that the transit switches form the core of the network and that, consequently, they must meet the very strict criteria of speed, reliability and modularity. It is also possible to conceive of switches having the dual function of end switches and transit switches.